Youngsters at Teddington School, west London, whose former pupils include actors Keira Knightley and Sean Pertwee, were given the script to study. There is racial abuse and a teacher is called “batty”, derogatory slang for gay. One of the main characters snarls at a schoolgirl: “Suck my ****.”

Mrs Stockford, 52, a former social worker, said her daughter Anna studied the play from last spring until Christmas.

She said: “I’m no prude but this play was absolutely saturated with swearing. I counted almost 400 expletives.

“On top of that the play deals with some very dark themes and includes racist, sexist and homophobic language. I think it is very irresponsible of the school to teach this kind of material to a class full of 14-year-olds. My daughter was very uncomfortable with the language so found it very difficult to act. She will likely be marked down for her GCSE drama as a result.

“I pointed out to the school that such a play would be regarded as unsuitable even for older teenagers and certainly wouldn’t be allowed on television. The only apology the school has made is for the fact parents weren’t consulted before their children started the play.”

Mogadishu, written by former teacher Vivienne Franzmann, premiered at the Royal Exchange in Manchester in 2011 before transferring to the Lyric Theatre in Hammersmith, London.

In the highly charged plot, London ­secondary school teacher Amanda splits up a fight involving black pupil Jason who pushes her to the floor.

She refuses to report the ­matter because she feels sorry for Jason whose mother committed suicide. However, she faces ­losing her job after Jason accuses her of pushing and racially ­abusing him.

Chris McGovern, chairman of the Campaign for Real Education, said yesterday: “Mogadishu’s excessive use of foul ­language and its treatment of such themes as racism, bullying, violence, self-harm and suicide may prove profoundly disturbing to some youngsters.”

Claude Knights, chief executive officer of Kidscape, said: “If such a text is sanctioned by a school there is a danger that this language will be seen as acceptable and that it will percolate into the ways the young people relate to one another. Why would we want to steer young minds back to the dark times when homophobia, sexism and racism were perpetuated through abhorrent verbal abuse?”

Jeremy Law, Teddington’s acting head, said: “The play deals with a lot of challenging contemporary themes and asks the audience to challenge and judge the values and behaviour of the protagonists. The responses from our ­students were very mature, thoughtful and well considered.

“Students allowed themselves to be moved by its themes rather than be hung up on the sometimes gritty vernacular.

“To imagine that it had done anything else would be to do a massive disservice to their ­intellect and their grasp of social and moral issues.”